1. Field of the Invention
The present invention relates to electrical connectors, particularly to self-locking, two-part electrical connectors which have means for preventing the connector halves from accidental disconnection.
2. Description of Prior Art
Electric appliances and tools, used nowadays for many purposes, derive their power from electrical outlets, to which the appliances are connected via electrical cords. A cord typically comprises a male plug and wire connecting it to the appliance or tool, while a female receptacle is usually associated with a wall outlet or another cord, such as an extension cord.
In use, the connection between the mating parts often becomes loose over a period of time, or they can be accidentally disconnected. At the best, this occurrence can be a nuisance, but in some cases it may have more serious consequencies, such as loss of valuable information from a computer, or creation of a hazardous condition. Therefore, it would be desirable to have two-part connectors with means for reliably locking the male and female parts against unintentional separation.
Heretofore, many such connectors have been known and used for connection of tools and appliances to the source of electric power. For example, U.S. Pat. No. 3,710,304 to J. Warner, et al., 1973, describes a female plug which has a pushbutton on the outer side of the plug body for engagement and disengagement and a toggle arrangement within the body for frictionally fixing prongs of the male plug from slipping out of the female receptacle. However, the Warner device has a complicated construction, a large number of moveable parts with pivotal connections, and, therefore, a limited number of engagement/disengagement cycles.
The above disadvantages have been eliminated in the self-locking, two-part electrical connector shown in U.S. Pat. No. 4,627,681 to D. Hong, 1986. One of the embodiments shown in that patent comprises a male plug, a female socket, and a spring-loaded moveable wedge mechanism in the socket for pressing the blades in the female socket against the prongs of the plug when the connector halves are mated. The spring-loaded wedge mechanism consists of a pushbutton located on the outer side of the female socket facing the mating male plug, and a wedge element inside the female socket which in the coupled position engages cam followers on the female blades and presses them tightly to the male plug prongs.
Although this connector has a rather simple construction, it is unreliable in operation, and will have a short life. It is unreliable because after withdrawal of the plug, the wedge element may remain jammed between the camming elements of the socket, and it has short life because the camming or wedging force is applied to contact blades of the socket, rather than directly to prongs of the plug. The contact blades of the socket are usually rigidly fixed or molded within the receptacle's body, i.e., they are not yieldable, as are the prongs of the plug, and therefore repeated deformations may lead to concentrations of stress, generation of fatigue stress, resulting in cracks and loose connections.
Other types of locking connectors have been proposed, such as the type where the male plug is inserted and then twisted to lock it in position. However, this "twist-lock" device required a special additional motion to lock it, its operation is affected by wear, it is sometimes unreliable in that the halves separate unintentionally, and expensive adaptors are required to attach it to most types of equipment.